1. Field of the Invention
This invention relates to a signal detecting method in autoradiography.
2. Description of the Prior Art
Autoradiography has been known as a method for obtaining locational information on radioactively labeled substances distributed in at least one-dimensional direction to form a row or rows on a support medium.
For instance, autoradiography comprises steps of: labeling organism-originating biopolymers such as proteins or nucleic acids with a radioactive element; resolving the radioactively labeled biopolymers, derivatives thereof, or cleavage products thereof (referred to hereafter as "radioactively labeled substances") on a gel support (support medium) through a resolving process such as electrophoresis to form a resolved pattern of the radioactively labeled substances (the resolved pattern is not visible); placing said gel support and a high-sensitivity type X-ray film together in layers for a certain period of time to expose said film and developing said film to give the autoradiograph of the resolved pattern as a visible image on the film; and obtaining the locational information on the radioactively labeled substances from said visible image. Further, the identification of the polymeric substances, determination of molecular weight of the polymeric substances and isolation of the polymeric substances can be performed based on the obtained locational information. The autoradiography has been effectively utilized for determining the base sequence of nucleic acids such as DNA.
In the autoradiography utilizing the above-mentioned radiographic process, the autoradiograph is analyzed through visual judgement of investigators. Instead of the above analytical method, a digital signal processing method for obtaining information on one-dimensional location of radioactively labeled substances in the form of symbols and/or numerals, which comprises reading out the visualized autoradiograph photoelectrically to give a digital signal and applying an appropriate signal processing to the digital signal, is described, for instance, in Japanese Patent Application No. 58(1983)-1336 (corresponding to U.S. patent application Ser. No. 06/568875 and European patent application No. 84100147.2). Said signal processing method comprises steps of: determining a one-dimensional scanning line (namely one-dimensional distribution direction of the radioactively labeled substances) for signal processing with respect to the obtained digital signal, and detecting sampling points on the scanning line. The term "scanning" in this method means the numeral scanning on the digital image data.
According to the above-mentioned signal processing method, the information on one-dimensional location of the radioactively labeled substances, which has been conventionally obtained through visual judgement by investigators, can be obtained automatically and accurately in the desired form such as symbols and/or numerals. Consequently, the above-mentioned signal processing method improves the accuracy of locational information and brings about an increase of the amount of information obtained.
Another signal processing method in the autoradiography utilizing the radiography, which comprises determining the scanning line for detecting sampling points with respect to the obtained digital signal, is described in Japanese patent application No. 58(1983)-1337 (the content of which is disclosed in U.S. patent application Ser. No. 568,873 and European Patent Application No. 84100149.8).
In any signal processing method described above, the one-dimensional distribution direction (scanning line on the digital image data for detecting sampling points) of the radioactively labeled substances is determined, after the digital signal corresponding to the autoradiograph having the locational information on the radioactively labeled substances is obtained by photoelectrically reading out the autoradiograph visualized on the radiosensitive material. Therefore, the obtained digital signal is initially stored in a memory of a signal processing circuit and subsequently the digital signals is selectively taken out of the memory according to the signal processing operation, so as to determine the one-dimensional distribution direction of the radioactively labeled substances.
More in detail, the read-out of the radiosensitive material is carried out over its entire surface and the digital image data are inevitably obtained even on a vacant area of the sheet which does not give any locational information on radioactively labeled substances. That is, all of the digital signal which is obtained by detecting on the entire surface of the radiosensitive material should be temporally stored in the memory of the signal processing circuit, and thus the memory requires a great capacity for storing it.
Additionally, the photoelectrically read-out operation on the radiosensitive material requires a long period of time, because the operation should be carried out over the entire surface thereof.